ISO 



conspicuous, are the two strong keels or ridges on the carapace. 

 Indications of such keels are also seen in other species, but 

 they are far from reaching the development which they do in 

 the Greenland species. In the following I shall only state the 

 most evident differences between C. bicarinatum and the other 

 species of the genus Coeloma with which I am acquainted. 



C. vigil Milne Edwards. In the museum of Göttingen 

 1 saw a specimen of this species from Laverda. It was 

 in a rather bad state of preservation. According to this spe- 

 cimen C. vigil seems to differ in the following particulars: 

 Its form is higher, less narrowing towards the posterior region, 

 a little less inflated. The front is narrower in proportion. The 

 anterio-lateral margins are placed somewhat more steeply; they 

 only carry four spines on each side. The two keels on the 

 carapace are much less pronounced, and carry two nodes which 

 are indistinct and placed rather near each other. The surface 

 carries rather coarse tubercles which are placed close together. 



C. balticum Schlüter. In addition to Noetling's very detailed 

 description I know this species from a specimen in the museum 

 of Göttingen. The anterio-lateral margins are here compara- 

 tively longer, and only carry four spines on each side. The 

 two keels on the metabranchial lobes are missing, or are at any 

 rate only very indistinctly indicated. The granulations on the 

 carapace are considerably coarser than in C. bicarinatum sp. 



C. granulosiim Milne Edwards has a narrower front, and 

 a much longer anterior margin. The anterio-lateral margins 

 run in almost the same direction as the posterio-lateral ones. 

 Only four spines are found on each of the anterio-lateral 

 margins. No keels on the metabranchial lobes. 



С Reidemeisteri Noetling. I only know this species from 

 Noetling's description. It is said to belong to his group Laeves, 

 and is ditïerent from C. balticum Schlüter with which species 

 it was formerly identified. This circumstance presumably permits 



